The paint recovery process of this invention provides an economical method for recovery and re-using latex paint lost during product change-overs in the plant manufacturing equipment. Lost paint is that part of the paint batch which remains on the sides of the mixing and thindown tanks as well as interconnecting process piping after the completed paint product has been discharged for filling of consumer containers. Typically the lost paint comprises about 1% by volume per batch. During product change over, filling equipment, piping and thindown tanks must be rinsed with water to remove residual latex paint before starting the next batch of paint. Prior to this invention, the residual paint typically was flushed out of the processing equipment and filling system with water, collected, and then flocculated. The flocculated solid waste was then filtered generating inordinate amounts of filter cake and solid paint wastes. The treated paint solids were landfilled while the effluent water was further biologically treated and/or sent to a publicly operated treatment works. Hence, the lost paint solids generated by cleaning processing equipment and related systems during product change over can represent significant amounts of lost product in addition to posing substantial environmental disposal problems. A large latex paint processing facility, for instance, can generate lost paint product valued in excess of one-half million dollars annually due to these losses.
It now has been found that latex paint processing waste collected by cleaning plant equipment with water can be collected as a dilute slurry, processed in a separator unit adapted to separate the waste slurry into a concentrated paint discharge resulting in increased solids content of at least delta 5% and preferably containing about 40% to 50% by weight paint solids in conjunction with a water distillate discharge comprising above about 99% by weight water. The concentrated paint can be recovered directly as usable paint while the water distillate can be recycled for subsequent cleaning or reused as make up water in a new batch of latex paint. The preferred separator unit comprises an evaporator separation process under vacuum so that evaporation temperatures can be minimized to avoid thermal degradation of the recovered paint product. The recovery process of this invention effectively eliminates the need for landfilling solids and disposal of dirty waste water according to conventional processes. This invention provides an effective and efficient paint recovery process where latex paint diluted with water is separated into a concentrated latex paint stream and a water stream. The process is particularly useful in recovering waste latex paint accumulated during the cleaning of latex paint manufacturing equipment and interconnecting pipes during product change over. These and other advantages of this invention will become more apparent by referring to the drawings and detailed description of the invention.